1. Field of the Invention
The present invention relates generally to devices and methods for storing and transferring thermal energy for cooling and heating processes. The present invention relates more specifically to the structure and composition of a device for the storage and transfer of latent heat energy for the purposes of rapidly and controllably cooling or heating objects and environments.
2. Description of the Related Art
The transfer and storage of thermal energy has generally been accomplished through the use of mechanical compressors and the like that convert mechanical energy into thermal energy through the compression and expansion of appropriate compounds such as chloro-fluorocarbons. Problems with these compounds and their effect on the environment, however, have led those in the field to examine alternative compounds for use in mechanical compressor devices and to look to other means for the storage and transfer of thermal energy. While solid state thermal energy devices have been known for some time, their use has generally been limited because of their inability to either rapidly deliver the thermal energy required or to store that energy over time in a device that can, thereafter, rapidly deliver it in large quantities. One common solid state thermal energy device known as the Peltier element is capable of transferring thermal energy into or out of an object or environment that it is in contact with, but unfortunately these operate efficiently only at a relatively slow rate. Such Peltier element devices lend themselves to applications where either the gradual transfer of thermal energy is desired or a device is in place for the storage of thermal energy for later use.
There have been a number of attempts in the past to create materials, devices, and methods for the rapid cooling or heating of objects or environments. The following patents are representative of these efforts.
U.S. Pat. No. 4,823,863 issued to Nakajima et al. on Apr. 25, 1989, entitled THERMAL CONDUCTION DEVICE, describes the structure of an interface between a heat generating element, typically an electronic component, and a heat sink element. This interface includes a porous layer made of sintered metallic particles that form a rigid sponge-like structure within which a heat conductive oil is retained.
U.S. Pat. No. 5,061,630 issued to Knopf et al. on Oct. 29, 1991, entitled LABORATORY APPARATUS FOR OPTIONAL TEMPERATURE-CONTROLLED HEATING AND COOLING, describes the use of small particles of a heat conducting solid such as graphite or metal powder, or spheres of metal or glass, that serves both to conduct heat and to stabilize vessels that are placed within the particles. The device uses a Peltier element in contact with a metallic core that in turn is in contact with the small particles.
U.S. Pat. No. 2,401,797 issued to Rasmussen on Jun. 11, 1946, entitled HEAT EXCHANGER, describes another use of sintered metal as the medium for a heat exchanger. In Rasmussen, a number of copper tubes pass through the sintered, highly porous block of bronze. The sintering is carried out after the tubes are imbedded in the bronze powder so that bonding is accomplished between the sintered metal and the copper tubes.
U.S. Pat. No. 4,439,337 issued to Nimerick et al. on Mar. 27, 1984, entitled COMPOSITION AND METHOD FOR PREVENTING FREEZING TOGETHER OF VARIOUS SURFACES, describes a freeze "releasing" agent that contains at least three water soluble components, including: (1) a polyhydroxy compound or a monoalkyl ether thereof; (2) an organic non-volatile compound having at least one hydrophilic group, (2) being different than (1); (3) optionally a salt which functions to lower the freezing point of water; (4) an organic polymer which functions to increase viscosity; and (5) water as a carrying fluid.
U.S. Pat. No. 4,987,896 issued to Nakamatsu on Jan. 29, 1991, entitled APPARATUS FOR INCREASING THE ACTIVITY OF THE HUMAN BRAIN, refers to the use of liquids having low freezing temperatures, and gives as examples a 50% aqueous solution of ethylene glycol, propylene glycol, agar solution or the like.
U.S. Pat. No. 4,813,283 issued to Craubner on Mar. 21, 1989, entitled DENSITY MEASURING APPARATUS, describes the use of a liquid for improving the thermal coupling between a buoyant fluid and a temperature sensor. In the case of certain low temperature experiments, the coupling fluid is described as having a sufficiently low freezing point, and may comprise methanol, ethanol, toluene, isopentene and other suitable liquids.
U.S. Pat. No. 3,381,818 issued to Sachar et al. on May 3, 1983, entitled POROUS FILM HEAT TRANSFER, describes a composition intended for use as a heat sink film to be coated on the surface of an integrated electronic circuit. The film is composed of a porous metal, preferably aluminum.
U.S. Pat. No. 4,981,172 issued to Haerle on Jan. 1, 1991, entitled MECHANISM FOR HEAT TRANSFER, describes a heat transfer device that is coated at least in part with metal shavings, metal wires, or coarse metal powder made of thermally conducted material and then sintered. Haerle also describes initially distributing the metallic powder by shaking, by introduction over a sticky liquid, or by electrical and/or magnetic effects.
U.S. Pat. No. 4,996,847 issued to Zickler on Mar. 5, 1991, entitled THERMOELECTRIC BEVERAGE COOLER AND DISPENSER, describes a system that employs a Peltier element in the cooling of a liquid dispensed from a beverage bottle inserted into the top of the device. This device employs the Peltier element in conjunction with a honeycomb array of beverage passageways to quickly cool the liquid.
U.S. Pat. No. 4,719,968 issued to Speros on Jan. 19, 1988, entitled HEAT EXCHANGER, describes a heat exchange mass made up of particles of crystalline carbon, copper and aluminum. The Speros heat exchanger is described as taking a cylindrical or planar configuration and may be contained within metal conduits or, in the case of solar radiation, transparent or translucent enclosures.
U.S. Pat. No. 5,314,586 issued to Chen on May 24, 1994, entitled PURIFYING AND ENERGY-SAVING WATER FOUNTAIN CAPABLE OF SUPPLYING ICY, WARM AND HOT DISTILLED WATER, discloses an electronic chilling device that consists of radiating fins, a Peltier element and condensing fins. The patent also describes the use of a eutectic melting salt as a thermal medium within which a coil cooling pipe is positioned.
U.S. Pat. No. 3,088,289 issued to Alex on May 7, 1963, entitled WATER COOLER, describes a Peltier element positioned between an array of radiating fins or channels, and an interior cooling plate that surrounds the liquid being cooled. Insulation around the entire structure prevents heat loss after cooling.
The above patents describe systems that in general fail as solid state thermal energy mechanisms capable of large scale useful application. The use of solid state cooling and heating devices has generally been limited to very small applications where high rates of energy transfer are not required. Most attempts in the past to create thermal storage devices of significant size (from the standpoint of the quantity of heat energy they can retain) and with substantial transfer rates (from the standpoint of how fast they can absorb or deliver thermal energy), have been limited to mechanical devices such as compressors that are subject to all the disadvantages associated with any such non-solid state configurations.